skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Nanoscale Visualization of Reversible Redox Pathways in Lithium-Sulfur Battery Using In Situ AFM-SECM
Deducing the electrochemical activity of intermediates and providing materials solution to alter their reaction pathways holds the key for developing advanced energy storage systems such as lithium-sulfur (Li-S) batteries. Herein, we provide mechanistic perspectives of the substrate guided reaction pathways of intermediate polysulfides and their correlation to the redox activity of discharge end products using In Situ atomic force microscopy-based scanning electrochemical microscopy (AFM-SECM) coupled Raman spectroscopy at nanoscale spatiotemporal resolution. In Situ SECM intermediate detection along with Raman analysis at the electrode/electrolyte interface reveals that the precipitation of Li 2 S can occur via an electrochemically active lithium disulfide (Li 2 S 2 ) intermediate step. With a detailed spectro-electrochemical and morphological mapping, we decipher that the substrate-dependent Li 2 S 2 formation adversely affects the Li 2 S oxidation in the subsequent cycles, thereby reducing the round-trip efficiency and overall performance of the cell. The present study provides nanoscale-resolved information regarding the polysulfide reaction pathways in Li-S batteries with respect to the electrode structure and its properties.  more » « less
Award ID(s):
1751472
PAR ID:
10391934
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Journal of The Electrochemical Society
Volume:
169
Issue:
6
ISSN:
0013-4651
Page Range / eLocation ID:
060501
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; (, Angewandte Chemie International Edition)
    Abstract Due to its outstanding safety and high energy density, all‐solid‐state lithium‐sulfur batteries (ASLSBs) are considered as a potential future energy storage technology. The electrochemical reaction pathway in ASLSBs with inorganic solid‐state electrolytes is different from Li‐S batteries with liquid electrolytes, but the mechanism remains unclear. By combining operando Raman spectroscopy and ex situ X‐ray absorption spectroscopy, we investigated the reaction mechanism of sulfur (S8) in ASLSBs. Our results revealed that no Li2S8,Li2S6,and Li2S4were formed, yet Li2S2was detected. Furthermore, first‐principles structural calculations were employed to disclose the formation energy of solid state Li2Sn(1≤n≤8), in which Li2S2was a metastable phase, consistent with experimental observations. Meanwhile, partial S8and Li2S2remained at the full lithiation stage, suggesting incomplete reaction due to sluggish reaction kinetics in ASLSBs. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Journal of The Electrochemical Society)
    Na-ion batteries (NIBs) are proposed as a promising candidate for beyond Li-ion chemistries, however, a key challenge associated with NIBs is the inability to achieve intercalation in graphite anodes. This phenomenon has been investigated and is believed to arise due to the thermodynamic instability of Na-intercalated graphite. We have recently demonstrated theoretical calculations showing it is possible to achieve thermodynamically stable Na-intercalated graphene structures with a fluorine surface modifier. Here, we present experimental evidence that Na + intercalation is indeed possible in fluorinated few-layer graphene (F-FLG) structures using cyclic voltammetry (CV), ion-sensitive scanning electrochemical microscopy (SECM) and in situ Raman spectroscopy. SECM and Raman spectroscopy confirmed Na + intercalation in F-FLG, while CV measurements allowed us to quantify Na-intercalated F-FLG stoichiometries around NaC 14–18 . These stoichiometries are higher than the previously reported values of NaC 186 in graphite. Our experiments revealed that reversible Na + ion intercalation also requires a pre-formed Li-based SEI in addition to the surface fluorination, thereby highlighting the critical role of SEI in controlling ion-transfer kinetics in alkali-ion batteries. In summary, our findings highlight the use of surface modification and careful study of electrode-electrolyte interfaces and interphases as an enabling strategy for NIBs. 
    more » « less
  3. ; ; ; ; (, Nature Communications)
    Abstract The complex interplay and only partial understanding of the multi-step phase transitions and reaction kinetics of redox processes in lithium–sulfur batteries are the main stumbling blocks that hinder the advancement and broad deployment of this electrochemical energy storage system. To better understand these aspects, here we report operando confocal Raman microscopy measurements to investigate the reaction kinetics of Li–S redox processes and provide mechanistic insights into polysulfide generation/evolution and sulfur deposition. Operando visualization and quantification of the reactants and intermediates enabled the characterization of potential-dependent rates during Li–S redox and the linking of the electronic conductivity of the sulfur-based electrode and concentrations of polysulfides to the cell performance. We also report the visualization of the interfacial evolution and diffusion processes of different polysulfides that demonstrate stepwise discharge and parallel recharge mechanisms during cell operation. These results provide fundamental insights into the mechanisms and kinetics of Li–S redox reactions. 
    more » « less
  4. ; ; ; ; (, ChemElectroChem)
    Abstract The solid electrolyte interphase (SEI) is a dynamic, electronically insulating film that forms on the negative electrode of Li+batteries (LIBs) and enables ion movement to/from the interface while preventing electrolyte breakdown. However, there is limited comparative understanding of LIB SEIs with respect to those formed on Na+and K+electrolytes for emerging battery concepts. We used scanning electrochemical microscopy (SECM) for the in situ interfacial analysis of incipient SEIs in Li+, K+and Na+electrolytes formed on multi‐layer graphene. Feedback images using 300 nm SECM probes and ion‐sensitive measurements indicated a superior passivation and highest cation flux for a Li+‐SEI in contrast to Na+and K+‐SEIs. Ex situ X‐ray photoelectron spectroscopy indicated significant fluoride formation for only Li+and Na+‐SEIs, enabling correlation to in situ SECM measurements. While SEI chemistry remains complex, these electroanalytical methods reveal links between chemical variables and the interfacial properties of materials for energy storage. 
    more » « less
  5. ; ; ; (, Materials Chemistry Frontiers)
    A scanning electrochemical microscope (SECM) can directly monitor electrochemical processes at interfaces of electrodes and electrolytes and has been used as an analytical tool for lithium-ion battery (LIB) studies. Through SECM, we can visualize the electrochemical reactivities of active species in LIBs in-situ during cycling. This review begins with introducing SECM-based LIB research and then summarizes the working mechanism and operating modes of the technique as well as combinations of SECM with other techniques for LIB studies. We review the results with a focus on the interfacial properties, surface reactions and electrochemical activity of different electrode materials for LIBs. The investigations of battery degradation, kinetic parameters and electrolyte swelling by SECM are also discussed. Finally, the current limitations and perspectives are also described regarding future developments. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email